Modal Analysis of a Vertical Rectangular Plate Semi-Submerged in Water with Different Boundary Conditions

The structure of marine vessels is usually being subjected to the dynamic loading conditions of sea-surface waves. The dynamics and vibrational characteristics of such structures is expected to be affected by sea environmental loadings. In this paper, a rectangular plate, that was immersed with water at different immersion depths and different boundary conditions was numerically analyzed by the Abaqus software, and the results have been presented and discussed in details. For validation the numerical method, the effects of immersion depth on the natural frequency of circular plate, which is parallel to the free surface of water, have been investigated experimentally and numerically. By evaluating 81 extracted vibrational modes, it became clear that a natural drop in natural frequencies begins with a rise in the fluid's height from a specific position, which is directly related to the type of boundary conditions. In the modal analysis of structures, it can be admitted that the major decreasing frequency due to increased mass is caused by one-way contact of the fluid and the structure and then, if the other side of the structure is in contact with the fluid, it will have a very small effect on the natural frequency reduction, which is clearly apparent in this study.